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(四) 紫外吸收光譜对于C_8以前芳香烃的定量分析汽油餾分中C_8以前芳烃的異构物为数較少,共有六个。各个单体芳烃在工业中已有一定用途,故要求一个快速的分析方法也較迫切。我們参考文献[7]、[10]使用石英分光光度計,以異辛烷为溶剂,对各个純的八碳以前芳烃进行了紫外吸收光譜的测定,並选择了表5所列各波长作为测定点。在指定波长与狭縫宽度时,各个芳烃的消光系数也皆列于表5中,芳香烃在紫外区的吸收谱线强度与浓度間基本上是符合比耳氏定律的,可以用式(2)进行計算。从表5可以看出甲苯与乙基苯的吸收光譜十分相像,故一般用蒸餾法預先将苯和甲苯与二甲苯分开,然后再分别测定。表6为苯与甲苯在汽油中已知重量百分数与测
(IV) UV Absorption Spectroscopy for the Quantitative Analysis of C_8 Aromatic Hydrocarbons There are six isoforms of aromatics prior to C_8 in the gasoline fraction. Aromatic hydrocarbons in various industries have been used for some purposes, it requires a more rapid analysis methods are more urgent. We reference [7], [10] the use of quartz spectrophotometer, isooctane as solvent, each pure eight-carbon before the determination of aromatics UV absorption spectra and selected the wavelength listed in Table 5 as a measure point. The extinction coefficients of each aromatics are also given in Table 5 for a given wavelength and slit width. Aromatic hydrocarbons strongly conform to Beer’s law between the intensity and the concentration of the absorption line in the UV region, )Calculation. As can be seen from Table 5, toluene and ethylbenzene absorption spectra are very similar, it is generally pre-distillation of benzene and toluene and xylene separated, and then were measured. Table 6 for benzene and toluene in gasoline known weight percent and measured